Simplify the following expression: ${3(3n-7)-(-2-5n)}$
Solution: Distribute the ${3}$ into the first set of parentheses: $ {3(}\gray{3n-7}{)} - (-2-5n) $ $ {9n-21} - (-2-5n) $ The minus sign in front of the parentheses means we multiply each term inside the parentheses by ${-1}$ $ 9n-21 {-1(}\gray{-2-5n}{)} $ $ 9n-21 + {2+5n} $ Rewrite the expression to group the ${n}$ terms and numeric terms: $ {9n + 5n} {-21 + 2}$ Combine the ${n}$ terms: $ {14n} {-21 + 2}$ Combine the numeric terms: $ {14n} {-19}$ The simplified expression is $14n-19$